Magnetic sensor and an integrated circuit

ABSTRACT

The present teaching relates to a magnetic sensor residing in a housing. The magnetic sensor includes an input port and an output port, both extending from the housing, wherein the input port is to be connected to an external alternating current (AC) power supply. The magnetic sensor also includes an electric circuit which comprises an output control circuit coupled with the output port and configured to be at least responsive to a magnetic induction signal and the external AC power supply to control the magnetic sensor to operate in a state in which a load current flows through the output port. The magnetic induction signal is indicative of at least one characteristic of an external magnetic field detected by the electrical circuit and the operating frequency of the magnetic sensor is positively proportional to the frequency of the external AC power supply.

CROSS REFERENCE TO RELATED APPLICATIONS

This non-provisional patent application is a continuation-in-part ofU.S. patent application Ser. No. 14/822,353, which claims priority toChinese Patent Application No. 201410390592.2, filed on Aug. 8, 2014 andto Chinese Patent Application No. 201410404474.2, filed on Aug. 15,2014. In addition, this non-provisional patent application claimspriority under the Paris Convention to PCT Patent Application No.PCT/CN2015/086422, filed with the Chinese Patent Office on Aug. 7, 2015,to Chinese Patent Application No. CN 201610203682.5, filed with theChinese Patent Office on Apr. 1, 2016, and to Chinese Patent ApplicationNo. CN 201610392501.8, filed with the Chinese Patent Office on Jun. 2,2016 all of which are incorporated herein by reference in theirentirety.

BACKGROUND

1. Technical Field

The present teaching relates to a field of circuit technology. Inparticular, the present teaching relates to a magnetic sensor. Thepresent teaching further relates to a driver for a low-power permanentmagnetic motor.

2. Discussion of Technical Background

During starting of a synchronous motor, the stator produces analternating magnetic field causing the permanent magnetic rotor to beoscillated. The amplitude of the oscillation of the rotor increasesuntil the rotor begins to rotate, and finally the rotor is acceleratedto rotate in synchronism with the alternating magnetic field of thestator. To ensure the starting of a conventional synchronous motor, astarting point of the motor is set to be low, which results in that themotor cannot operate at a relatively high working point, thus theefficiency is low. In another aspect, the rotor cannot be ensured torotate in a same direction every time since a stop or stationaryposition of the permanent magnetic rotor is not fixed. Accordingly, inapplications such as a fan and water pump, the impeller driven by therotor has straight radial vanes, which results in a low operationalefficiency of the fan and water pump.

FIG. 1 illustrates a conventional drive circuit for a synchronous motor,which allows a rotor to rotate in a same predetermined direction inevery time it starts. In the circuit, a stator winding 1 of the motor isconnected in series with a TRIAC between two terminals M and N of an ACpower source VM, and an AC power source VM is converted by a conversioncircuit DC into a direct current voltage and the direct current issupplied to a position sensor H. A magnetic pole position of a rotor inthe motor is detected by the position sensor H, and an output signal Vhof the position sensor H is connected to a switch control circuit PC tocontrol the bidirectional thyristor T.

FIG. 2 illustrates a waveform of the drive circuit. It can be seen fromFIG. 2 that, in the drive circuit, no matter the bidirectional thyristorT is switched on or off, the AC power source supplies power for theconversion circuit DC so that the conversion circuit DC constantlyoutputs and supplies power for the position sensor H (referring to asignal VH in FIG. 2). In a low-power application, in a case that the ACpower source is commercial electricity of about 200V, the electricenergy consumed by two resistors R2 and R3 in the conversion circuit DCis more than the electric energy consumed by the motor.

The magnetic sensor applies Hall effect, in which, when current I runsthrough a substance and a magnetic field B is applied in a positiveangle with respect to the current I, a potential difference V isgenerated in a direction perpendicular to the direction of current I andthe direction of the magnetic field B. The magnetic sensor is oftenimplemented to detect the magnetic polarity of an electric rotor.

As the circuit design and signal processing technology advances, thereis a need to improve the magnetic sensor and the implemented IC for theease of use and accurate detection.

SUMMARY

The present teaching provides a magnetic sensor and application(s)thereof. In one embodiment, the present teaching discloses a magneticsensor that comprises a housing, an input and an output port, bothextending from the housing, and an electrical circuit. The input port isconnected to an external alternating current (AC) power supply. Theelectrical circuit includes an output control circuit coupled with theoutput port and configured to be at least responsive to a magneticinduction signal to control the magnetic sensor to operate in at leastone of a first state and a second state. In the first state, a loadcurrent flows in a first direction from the output port to outside ofthe magnetic sensor. In the second state, a load current flows in asecond direction opposite of the first direction from outside of themagnetic sensor into the magnetic sensor via the output port. Theoperating frequency of the magnetic sensor is positively proportional tothe frequency of the external AC power supply.

In a different embodiment, the present teaching discloses a magneticsensor that includes a housing, an input port extending from the housingand coupled with an external AC power supply, an output port extendingfrom the housing, and an electrical circuit. The electrical circuitcomprises an output control circuit coupled with the output port andconfigured to be at least responsive to a magnetic induction signal andthe external AC power supply to control the magnetic sensor to operatein a state in which a load current flows through the output port. Themagnetic induction signal is indicative of at least one characteristicof an external magnetic field detected by the electrical circuit and theoperating frequency of the magnetic sensor is positively proportional tothe frequency of the external AC power supply.

In another different embodiment, the present teaching discloses anintegrated circuit, which includes an input port and an output port,wherein the input port is to be connected to an external AC powersupply, and an electrical circuit. The electrical circuit comprises anoutput control circuit coupled with the output port and configured to beat least responsive to a detected signal to control the integratedcircuit to operate in at least one of a first and a second state. In thefirst state, a load current flows in a first direction from the outputport to outside of the integrated circuit. In the second state, a loadcurrent flows in a second direction opposite of the first direction fromoutside of the integrated circuit into the integrated circuit via theoutput port. The operating frequency of the integrated circuit ispositively proportional to the frequency of the external AC powersupply.

In yet another embodiment, the present teaching discloses a motorassembly, which comprises a motor configured to operate based on an ACpower supply, a magnetic sensor configured to detect a magnetic fieldgenerated by the motor and operate in an operating state determinedbased on the detected magnetic field, and a bi-directional AC switchserially coupled with the motor and configured to control the motorbased on the operating state of the magnetic sensor. The magnetic sensorincludes an input port and an output port, wherein the input port iscoupled with the external AC power supply and the output port is coupledwith a control terminal of the bi-directional AC switch and anelectrical circuit which comprises an output control circuit configuredto be at least responsive to a magnetic induction signal, indicative ofat least one characteristic of the magnetic field, to control themagnetic sensor to operate in at least one of a first state and a secondstate. In operation, in the first state, a load current flows in a firstdirection from the output port to the bi-directional AC switch. In thesecond state, a load current flows in a second direction opposite of thefirst direction from the bi-directional AC switch to the magnetic sensorvia the output port. The operating frequency of the magnetic sensor ispositively proportional to the frequency of the external AC powersupply.

BRIEF DESCRIPTION OF THE DRAWINGS

The methods, systems, and/or programming described herein are furtherdescribed in terms of exemplary embodiments. These exemplary embodimentsare described in detail with reference to the drawings. Theseembodiments are non-limiting exemplary embodiments, in which likereference numerals represent similar structures throughout the severalviews of the drawings, and wherein:

FIG. 1 illustrates a prior art drive circuit for a synchronous motor,according to an embodiment of the present teaching;

FIG. 2 illustrates a waveform of the drive circuit shown in FIG. 1;

FIG. 3 illustrates a diagrammatic representation of a synchronous motor,according to an embodiment of the present teaching;

FIG. 4 illustrates a block diagram of a drive circuit for a synchronousmotor, according to an embodiment of the present teaching;

FIG. 5 illustrates a drive circuit for a synchronous motor, according toan embodiment of the present teaching;

FIG. 6 illustrates a waveform of the drive circuit shown in FIG. 5;

FIGS. 7 to 10 illustrate different embodiments of a drive circuit of asynchronous motor, according to an embodiment of the present teaching;

FIG. 11 illustrates an exemplary diagram of a magnetic sensor 1105according to an embodiment of the present teaching;

FIG. 12 illustrates an exemplary diagram of the magnetic sensor 1105according to a different embodiment of the present teaching;

FIG. 13 illustrates an exemplary diagram of the magnetic sensor 1105according to yet another embodiment of the present teaching;

FIG. 14 illustrates an exemplary implementation of the output controlcircuit 1120 according to an embodiment of the present teaching;

FIG. 15 illustrates an exemplary implementation of the output controlcircuit 1120 according to another embodiment of the present teaching;

FIG. 16 illustrates another exemplary diagram of the magnetic sensor1105 according to yet another embodiment of the present teaching;

FIG. 17 illustrates an exemplary diagram of the rectifier 1150 accordingto an embodiment of the present teaching;

FIG. 18 illustrates an exemplary diagram of the magnetic sensor 1105according to yet another embodiment of the present teaching;

FIG. 19 illustrates an exemplary implementation circuit of a part of themagnetic sensor 1105 according to yet another embodiment of the presentteaching;

FIG. 20 illustrates another embodiment of the output control circuit1120 in connection with the state control circuit 1140;

FIG. 21 is a flowchart of an exemplary method of signal processingperformed by the magnetic sensor 1105, according to an embodiment of thepresent teaching;

FIG. 22 illustrates an exemplary diagram of a motor assembly 2200incorporating the magnetic sensor discussed herein, according to anembodiment of the present teaching;

FIG. 23 illustrates an exemplary diagram of a motor 2300 according to anembodiment of the present teaching; and

FIG. 24 illustrates the waveforms of an output voltage from an AC powersupply 1610 and the rectifier bridge 1150, respectively, according to anembodiment of the present teaching.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details are setforth by way of examples in order to provide a thorough understanding ofthe relevant teachings. However, it should be apparent to those skilledin the art that the present teachings may be practiced without suchdetails. In other instances, well known methods, procedures, systems,components, and/or circuitry have been described at a relativelyhigh-level, without detail, in order to avoid unnecessarily obscuringaspects of the present teachings.

Throughout the specification and claims, terms may have nuanced meaningssuggested or implied in context beyond an explicitly stated meaning.Likewise, the phrase “in one embodiment/example” as used herein does notnecessarily refer to the same embodiment and the phrase “in anotherembodiment/example” as used herein does not necessarily refer to adifferent embodiment. It is intended, for example, that claimed subjectmatter include combinations of example embodiments in whole or in part.

In general, terminology may be understood at least in part from usage incontext. For example, terms, such as “and”, “or”, or “and/or,” as usedherein may include a variety of meanings that may depend at least inpart upon the context in which such terms are used. Typically, “or” ifused to associate a list, such as A, B or C, is intended to mean A, B,and C, here used in the inclusive sense, as well as A, B or C, here usedin the exclusive sense. In addition, the term “one or more” as usedherein, depending at least in part upon context, may be used to describeany feature, structure, or characteristic in a singular sense or may beused to describe combinations of features, structures or characteristicsin a plural sense. Similarly, terms, such as “a,” “an,” or “the,” again,may be understood to convey a singular usage or to convey a pluralusage, depending at least in part upon context. In addition, the term“based on” may be understood as not necessarily intended to convey anexclusive set of factors and may, instead, allow for existence ofadditional factors not necessarily expressly described, again, dependingat least in part on context.

FIG. 3 schematically shows a synchronous motor according to anembodiment of the present invention. The synchronous motor 10 includes astator 12 and a permanent magnet rotor 14 rotatably disposed betweenmagnetic poles of the stator 12, and the stator 12 includes a statorcore 15 and a stator winding 16 wound on the stator core 15. The rotor14 includes at least one permanent magnet forming at least one pair ofpermanent magnetic poles with opposite polarities, and the rotor 14operates at a constant rotational speed of 60 f/p during a steady statephase in a case that the stator winding 16 is connected to an AC powersupply, where f is a frequency of the AC power supply and p is thenumber of pole pairs of the rotor.

Non-uniform gap 18 is formed between the magnetic poles of the stator 12and the permanent magnetic poles of the rotor 14 so that a polar axis Rof the rotor 14 has an angular offset a relative to a central axis S ofthe stator 12 in a case that the rotor is at rest. The rotor 14 may beconfigured to have a fixed starting direction (a clockwise direction inthis embodiment as shown by the arrow in FIG. 3) every time the statorwinding 16 is energized. The stator and the rotor each have two magneticpoles as shown in FIG. 3. It can be understood that, in otherembodiments, the stator and the rotor may also have more magnetic poles,such as 4 or 6 magnetic poles.

A position sensor 20 for detecting the angular position of the rotor isdisposed on the stator 12 or at a position near the rotor inside thestator, and the position sensor 20 has an angular offset relative to thecentral axis S of the stator. Preferably, this angular offset is also a,as in this embodiment. Preferably, the position sensor 20 is a Halleffect sensor.

FIG. 4 shows a block diagram of a drive circuit for a synchronous motoraccording to an embodiment of the present invention. In the drivecircuit 22, the stator winding 16 and the AC power supply 24 areconnected in series between two nodes A and B. Preferably, the AC powersupply 24 may be a commercial AC power supply with a fixed frequency,such as 50 Hz or 60 Hz, and a supply voltage may be, for example, 110V,220V or 230V. A controllable bidirectional AC switch 26 is connectedbetween the two nodes A and B, in parallel with the stator winding 16and the AC power supply 24. Preferably, the controllable bidirectionalAC switch 26 is a TRIAC, of which two anodes are connected to the twonodes A and B respectively. It can be understood that, the controllablebidirectional AC switch 26 alternatively may be two silicon controlrectifiers reversely connected in parallel, and control circuits may becorrespondingly configured to control the two silicon control rectifiersin a preset way. An AC-DC conversion circuit 28 is also connectedbetween the two nodes A and B. An AC voltage between the two nodes A andB is converted by the AC-DC conversion circuit 28 into a low voltage DC.The position sensor 20 may be powered by the low voltage DC output bythe AC-DC conversion circuit 28, for detecting the magnetic poleposition of the permanent magnet rotor 14 of the synchronous motor 10and outputting a corresponding signal. A switch control circuit 30 isconnected to the AC-DC conversion circuit 28, the position sensor 20 andthe controllable bidirectional AC switch 26, and is configured tocontrol the controllable bidirectional AC switch 26 to be switchedbetween a switch-on state and a switch-off state in a predetermined way,based on the magnetic pole position of the permanent magnet rotor whichis detected by the position sensor and polarity information of the ACpower supply 24 which may be obtained from the AC-DC conversion circuit28, such that the stator winding 16 urges the rotor 14 to rotate only inthe above-mentioned fixed starting direction during a starting phase ofthe motor. According to this embodiment of the present invention, in acase that the controllable bidirectional AC switch 26 is switched on,the two nodes A and B are shorted, the AC-DC conversion circuit 28 doesnot consume electric energy since there is no current flowing throughthe AC-DC conversion circuit 28, hence, the utilization efficiency ofelectric energy can be improved significantly.

FIG. 5 shows a circuit diagram of a drive circuit 40 for a synchronousmotor according to a first embodiment of the present disclosure. Thestator winding 16 of the synchronous motor is connected in series withthe AC power supply 24 between the two nodes A and B. A first anode T1of the TRIAC 26 is connected to the node A, and a second anode T2 of theTRIAC 26 is connected to the node B. The AC-DC conversion circuit 28 isconnected in parallel with the TRIAC 26 between the two nodes A and B.An AC voltage between the two nodes A and B is converted by the AC-DCconversion circuit 28 into a low voltage DC (preferably, low voltageranges from 3V to 18V). The AC-DC conversion circuit 28 includes a firstzener diode Z1 and a second zener diode Z2 which are reversely connectedin parallel between the two nodes A and B via a first resistor R1 and asecond resistor R2 respectively. A high voltage output terminal C of theAC-DC conversion circuit 28 is formed at a connection point of the firstresistor R1 and a cathode of the first zener diode Z1, and a low voltageoutput terminal D of the AC-DC conversion circuit 28 is formed at aconnection point of the second resistor R2 and an anode of the secondzener diode Z2. The voltage output terminal C is connected to a positivepower supply terminal of the position sensor 20, and the voltage outputterminal D is connected to a negative power supply terminal of theposition sensor 20. Three terminals of the switch control circuit 30 areconnected to the high voltage output terminal C of the AC-DC conversioncircuit 28, an output terminal H1 of the position sensor 20 and acontrol electrode G of the TRIAC 26 respectively. The switch controlcircuit 30 includes a third resistor R3, a fifth diode D5, and a fourthresistor R4 and a sixth diode D6 connected in series between the outputterminal HI of the position sensor 20 and the control electrode G of thecontrollable bidirectional AC switch 26. An anode of the sixth diode D6is connected to the control electrode G of the controllablebidirectional AC switch 26. One terminal of the third resistor R3 isconnected to the high voltage output terminal C of the AC-DC conversioncircuit 28, and the other terminal of the third resistor R3 is connectedto an anode of the fifth diode D5. A cathode of the fifth diode D5 isconnected to the control electrode G of the controllable bidirectionalAC switch 26.

In conjunction with FIG. 6, an operational principle of the drivecircuit 40 is described. In FIG. 6, Vac indicates a waveform of voltageof the AC power supply 24, and lac indicates a waveform of currentflowing through the stator winding 16. Due to the inductive character ofthe stator winding 16, the waveform of current lac lags behind thewaveform of voltage Vac. V1 indicates a waveform of voltage between twoterminals of the first zener diode Z1, V2 indicates a waveform ofvoltage between two terminals of the second zener diode Z2, Vdcindicates a waveform of voltage between two output terminals C and D ofthe AC-DC conversion circuit 28, Ha indicates a waveform of a signaloutput by the output terminal H1 of the position sensor 20, and Hbindicates a rotor magnetic field detected by the position sensor 20. Inthis embodiment, in a case that the position sensor 20 is powerednormally, the output terminal HI outputs a logic high level in a casethat the detected rotor magnetic field is North, or the output terminalH1 outputs a logic low level in a case that the detected rotor magneticfield is South.

In a case that the rotor magnetic field Hb detected by the positionsensor 20 is North, in a first positive half cycle of the AC powersupply, the supply voltage is gradually increased from a time instant t0to a time instant t1, the output terminal H1 of the position sensor 20outputs a high level, and a current flows through the resistor R1, theresistor R3, the diode D5 and the control electrode G and the secondanode T2 of the TRIAC 26 sequentially. The TRIAC 26 is switched on in acase that a drive current flowing through the control electrode G andthe second anode T2 is greater than a gate triggering current Ig. Oncethe TRIAC 26 is switched on, the two nodes A and B are shorted, acurrent flowing through the stator winding 16 in the motor is graduallyincreased until a large forward current flows through the stator winding16 to drive the rotor 14 to rotate clockwise as shown in FIG. 3. Sincethe two nodes A and B are shorted, there is no current flowing throughthe AC-DC conversion circuit 28 from the time instant t1 to a timeinstant t2. Hence, the resistors R1 and R2 do not consume electricenergy, and the output of the position sensor 20 is stopped due to nopower is supplied. Since the current flowing through two anodes T1 andT2 of the TRIAC 26 is large enough (which is greater than a holdingcurrent Ihold), the TRIAC 26 is kept to be switched on in a case thatthere is no drive current flowing through the control electrode G andthe second anode T2. In a negative half cycle of the AC power supply,after a time instant t3, a current flowing through T1 and T2 is lessthan the holding current Ihold, the TRIAC 26 is switched off, a currentbegins to flow through the AC-DC conversion circuit 28, and the outputterminal HI of the position sensor 20 outputs a high level again. Sincea potential at the point C is lower than a potential at the point E,there is no drive current flowing through the control electrode G andthe second anode T2 of the TRIAC 26, and the TRIAC 26 is kept to beswitched off. Since the resistance of the resistors R1 and R2 in theAC-DC conversion circuit 28 are far greater than the resistance of thestator winding 16 in the motor, a current currently flowing through thestator winding 16 is far less than the current flowing through thestator winding 16 from the time instant t1 to the time instant t2 andgenerates very small driving force for the rotor 14. Hence, the rotor 14continues to rotate clockwise due to inertia. In a second positive halfcycle of the AC power supply, similar to the first positive half cycle,a current flows through the resistor R1, the resistor R3, the diode D5,and the control electrode G and the second anode T2 of the TRIAC 26sequentially. The TRIAC 26 is switched on again, and the current flowingthrough the stator winding 16 continues to drive the rotor 14 to rotateclockwise. Similarly, the resistors R1 and R2 do not consume electricenergy since the two nodes A and B are shorted. In the next negativehalf cycle of the power supply, the current flowing through the twoanodes T1 and T2 of the TRIAC 26 is less than the holding current Ihold,the TRIAC 26 is switched off again, and the rotor continues to rotateclockwise due to the effect of inertia.

At a time instant t4, the rotor magnetic field Hb detected by theposition sensor 20 changes to be South from North, the AC power supplyis still in the positive half cycle and the TRIAC 26 is switched on, thetwo nodes A and B are shorted, and there is no current flowing throughthe AC-DC conversion circuit 28. After the AC power supply enters thenegative half cycle, the current flowing through the two anodes T1 andT2 of the TRIAC 26 is gradually decreased, and the TRIAC 26 is switchedoff at a time instant t5. Then the current flows through the secondanode T2 and the control electrode G of the TRIAC 26, the diode D6, theresistor R4, the position sensor 20, the resistor R2 and the statorwinding 16 sequentially. As the drive current is gradually increased,the TRIAC 26 is switched on again at a time instant t6, the two nodes Aand B are shorted again, the resistors RI and R2 do not consume electricenergy, and the output of the position sensor 20 is stopped due to nopower is supplied. There is a larger reverse current flowing through thestator winding 16, and the rotor 14 continues to be driven clockwisesince the rotor magnetic field is South. From the time instant t5 to thetime instant t6, the first zener diode Z1 and the second zener diode Z2are switched on, hence, there is a voltage output between the two outputterminals C and D of the AC-DC conversion circuit 28. At a time instantt7, the AC power supply enters the positive half cycle again, the TRIAC26 is switched off when the current flowing through the TRIAC 26 crosseszero, and then a voltage of the control circuit is gradually increased.As the voltage is gradually increased, a current begins to flow throughthe AC-DC conversion circuit 28, the output terminal H1 of the positionsensor 20 outputs a low level, there is no drive current flowing throughthe control electrode G and the second anode T2 of the TRIAC 26, hence,the TRIAC 26 is switched off. Since the current flowing through thestator winding 16 is very small, nearly no driving force is generatedfor the rotor 14. At a time instant t8, the power supply is in thepositive half cycle, the position sensor outputs a low level, the TRIAC26 is kept to be switched off after the current crosses zero, and therotor continues to rotate clockwise due to inertia. According to anembodiment of the present invention, the rotor may be accelerated to besynchronized with the stator after rotating only one circle after thestator winding is energized.

In the embodiment of the present invention, by taking advantage of afeature of a TRIAC that the TRIAC is kept to be switched on althoughthere is no drive current flowing though the TRIAC once the TRIAC isswitched on, it is avoided that a resistor in the AC-DC conversioncircuit still consumes electric energy after the TRIAC is switched on,hence, the utilization efficiency of electric energy can be improvedsignificantly.

FIG. 7 shows a circuit diagram of a drive circuit 42 for a synchronousmotor according to an embodiment of the present disclosure. The statorwinding 16 of the synchronous motor is connected in series with the ACpower supply 24 between the two nodes A and B. A first anode T1 of theTRIAC 26 is connected to the node A, and a second anode T2 of the TRIAC26 is connected to the node B. The AC-DC conversion circuit 28 isconnected in parallel with the TRIAC 26 between the two nodes A and B.An AC between the two nodes A and B is converted by the AC-DC conversioncircuit 28 into a low voltage DC, preferably, a low voltage ranging from3V to 18V. The AC-DC conversion circuit 28 includes a first resistor RIand a full wave bridge rectifier connected in series between the twonodes A and B. The full wave bridge rectifier includes two rectifierbranches connected in parallel, one of the two rectifier branchesincludes a first diode D1 and a third diode D3 reversely connected inseries, and the other of the two rectifier branches includes a secondzener diode Z2 and a fourth zener diode Z4 reversely connected inseries, the high voltage output terminal C of the AC-DC conversioncircuit 28 is formed at a connection point of a cathode of the firstdiode D1 and a cathode of the third diode D3, and the low voltage outputterminal D of the AC-DC conversion circuit 28 is formed at a connectionpoint of an anode of the second zener diode Z2 and an anode of thefourth zener diode Z4. The output terminal C is connected to a positivepower supply terminal of the position sensor 20, and the output terminalD is connected to a negative power supply terminal of the positionsensor 20. The switch control circuit 30 includes a third resistor R3, afourth resistor R4, and a fifth diode D5 and a sixth diode D6 reverselyconnected in series between the output terminal H1 of the positionsensor 20 and the control electrode G of the controllable bidirectionalAC switch 26. A cathode of the fifth diode D5 is connected to the outputterminal H1 of the position sensor, and a cathode of the sixth diode D6is connected to the control electrode G of the controllablebidirectional AC switch. One terminal of the third resistor R3 isconnected to the high voltage output terminal C of the AC-DC conversioncircuit, and the other terminal of the third resistor R3 is connected toa connection point of an anode of the fifth diode D5 and an anode of thesixth diode D6. Two terminals of the fourth resistor R4 are connected toa cathode of the fifth diode D5 and a cathode of the sixth diode D6respectively.

FIG. 8 shows a circuit diagram of a drive circuit 44 for a synchronousmotor according to a further embodiment of the present invention. Thedrive circuit 44 is similar to the drive circuit 42 in the previousembodiment and, the drive circuit 44 differs from the drive circuit 42in that, the zener diodes Z2 and Z4 in the drive circuit 42 are replacedby general diodes D2 and D4 in the rectifier of the drive circuit 44. Inaddition, a zener diode Z7 is connected between the two output terminalsC and D of the AC-DC conversion circuit 28 in the drive circuit 44.

FIG. 9 shows a circuit diagram of a drive circuit 46 for a synchronousmotor according to further embodiment of the present invention. Thestator winding 16 of the synchronous motor is connected in series withthe AC power supply 24 between the two nodes A and B. A first anode T1of the TRIAC 26 is connected to the node A, and a second anode T2 of theTRIAC 26 is connected to the node B. The AC-DC conversion circuit 28 isconnected in parallel with the TRIAC 26 between the two nodes A and B.An AC voltage between the two nodes A and B is converted by the AC-DCconversion circuit 28 into a low voltage DC, preferably, a low voltageranging from 3V to 18V. The AC-DC conversion circuit 28 includes a firstresistor R1 and a full wave bridge rectifier connected in series betweenthe two nodes A and B. The full wave bridge rectifier includes tworectifier branches connected in parallel, one of the two rectifierbranches includes two silicon control rectifiers S1 and S3 reverselyconnected in series, and the other of the two rectifier branchesincludes a second diode D2 and a fourth diode D4 reversely connected inseries. The high voltage output terminal C of the AC-DC conversioncircuit 28 is formed at a connection point of a cathode of the siliconcontrol rectifier S1 and a cathode of the silicon control rectifier S3,and the low voltage output terminal D of the AC-DC conversion circuit 28is formed at a connection point of an anode of the second diode D2 andan anode of the fourth diode D4. The output terminal C is connected to apositive power supply terminal of the position sensor 20, and the outputterminal D is connected to a negative power supply terminal of theposition sensor 20. The switch control circuit 30 includes a thirdresistor R3, an NPN transistor T6, and a fourth resistor R4 and a fifthdiode D5 connected in series between the output terminal H1 of theposition sensor 20 and the control electrode G of the controllablebidirectional AC switch 26. A cathode of the fifth diode D5 is connectedto the output terminal H1 of the position sensor. One terminal of thethird resistor R3 is connected to the high voltage output terminal C ofthe AC-DC conversion circuit, and the other terminal of the thirdresistor R3 is connected to the output terminal H1 of the positionsensor. A base of the NPN transistor T6 is connected to the outputterminal H1 of the position sensor, an emitter of the NPN transistor T6is connected to an anode of the fifth diode D5, and a collector of theNPN transistor T6 is connected to the high voltage output terminal C ofthe AC-DC conversion circuit.

In this embodiment, a reference voltage may be input to the cathodes ofthe two silicon control rectifiers S1 and S3 via a terminal SC1, and acontrol signal may be input to control terminals of S1 and S3 via aterminal SC2. The rectifiers Si and S3 are switched on in a case thatthe control signal input from the terminal SC2 is a high level, or areswitched off in a case that the control signal input from the terminalSC2 is a low level. Based on the configuration, the rectifiers S1 and S3may be switched between a switch-on state and a switch-off state in apreset way by inputting the high level from the terminal SC2 in a casethat the drive circuit operates normally. The rectifiers Si and S3 areswitched off by changing the control signal input from the terminal SC2from the high level to the low level in a case that the drive circuitfails. In this case, the TRIAC 26, the conversion circuit 28 and theposition sensor 20 are switched off, to ensure the whole circuit to bein a zero-power state.

FIG. 10 shows a circuit diagram of a drive circuit 48 for a synchronousmotor according to another embodiment of the present invention. Thedrive circuit 48 is similar to the drive circuit 46 in the previousembodiment and, the drive circuit 48 differs from the drive circuit 46in that, the silicon control diodes S1 and S3 in the drive circuit 46are replaced by general diodes D1 and D3 in the rectifier of the drivecircuit 48, and a zener diode Z7 is connected between the two terminalsC and D of the AC-DC conversion circuit 28. In addition, in the drivecircuit 48 according to the embodiment, a preset steering circuit 50 isdisposed between the switch control circuit 30 and the TRIAC 26. Thepreset steering circuit 50 includes a first jumper switch J1, a secondjumper J2 switch and an inverter NG connected in series with the secondjumper switch J2. Similar to the drive circuit 46, in this embodiment,the switch control circuit 30 includes the resistor R3, the resistor R4,the NPN transistor T5 and the diode D6. One terminal of the resistor R4is connected to a connection point of an emitter of the transistor T5and an anode of the diode D6, and the other terminal of the resistor R4is connected to one terminal of the first jumper switch J1, and theother terminal of the first jumper switch J1 is connected to the controlelectrode G of the TRIAC 26, and the second jumper switch J2 and theinverter NG connected in series are connected across two terminals ofthe first jumper switch J1. In this embodiment, when the first jumperswitch J1 is switched on and the second jumper switch J2 is switchedoff, similar to the above embodiments, the rotor 14 still startsclockwise; when the second jumper switch J2 is switched on and the firstjumper switch J1 is switched off, the rotor 14 starts counterclockwise.In this case, a starting direction of the rotor in the motor may beselected by selecting one of the two jumper switches to be switched onand the other to be switched off. Therefore, in a case that a drivingmotor is needed to be supplied for different applications havingopposite rotational directions, it is just needed to select one of thetwo jumper switches J1 and J2 to be switched on and the other to beswitched off, and no other changes need to be made to the drive circuit,hence, the drive circuit according to this embodiment has goodversatility.

As discussed above, the position sensor 20 is configured for detectingthe magnetic pole position of the permanent magnet rotor 14 of thesynchronous motor 10 and outputting a corresponding signal. The outputsignal from the position sensor 20 represents some characteristics ofthe magnetic pole position such as the polarity of the magnetic fieldassociated with the magnetic pole position of the permanent magnet rotor14 of the synchronous motor 10. The detected magnetic pole position isthen used, by the switch control circuit 30, control the controllablebidirectional AC switch 26 to be switched between a switch-on state anda switch-off state in a predetermined way, based on, together with themagnetic pole position of the permanent magnet rotor, the polarityinformation of the AC power supply 24 which may be obtained from theAC-DC conversion circuit 28. It should be appreciated that the switchcontrol circuit 30 and the position sensor 20 can be realized viamagnetic sensing. Accordingly, the present teaching discloses a magneticsensor for magnetic sensing and control of a motor according to thesensed information.

More details are disclosed below on the magnetic sensor that comprisesaspects of both the position sensor 20 and the switch control circuit30. In describing the details of the magnetic sensor related to both theposition sensor 20 and the switch control circuit 30, the presentteaching of this continuation-in-part application more focuses onvarious details related to the realization of the switch control circuit30 via the magnetic sensor as disclosed herein.

The magnetic sensor according to the present teaching includes amagnetic field detecting circuit that can reliably detect a magneticfield and generate a magnetic induction signal indicative of certaincharacteristics of the magnetic field. The magnetic sensor as disclosedherein also includes an output control circuit that controls themagnetic sensor to operate in a state determined with respect to thepolarity of the magnetic field as well as that of an AC power supply. Asthe magnetic sensor is coupled with the bidirectional AC switch 26, themagnetic sensor can effectively regulate the operation of the motor viathe bidirectional AC switch. Further, the magnetic sensor in the presentteaching may be directly connected to a commercial/residential AC powersupply with no need for any additional A/D converting equipment. In thisway, the present disclosure of the magnetic sensor is suitable to beused in a wide range of applications.

Additional novel features associated with the magnetic sensor disclosedherein will be set forth in part in the description which follows, andin part will become apparent to those skilled in the art uponexamination of the following and the accompanying drawings or may belearned by production or operation of the examples. The novel featuresof the present teachings on a magnetic sensor may be realized andattained by practice or use of various aspects of the methodologies,instrumentalities and combinations set forth in the detailed examplesdiscussed below. The disclosed magnetic sensor, the signal processingmethod implemented in the magnetic sensor, and the electric motorincorporating the magnetic sensor and the signal processing methoddisclosed herein can be achieved realized based on any circuittechnology known to one of ordinary skill in the art including but notlimited to the integrated circuit and other circuit implementations.

FIG. 11 illustrates an exemplary diagram of a magnetic sensor 1105according to an embodiment of the present teaching. The magnetic sensor1105 includes a housing (not shown), a semiconductor substrate residingin the housing (not shown), a first input A1 1102, a second input A21104, an output port B 1106, and an electronic circuit 1100 residing onthe semiconductor substrate. The electronic circuit 1100 includes acontrol signal generation circuit 1110 and an output control circuit1120 coupled to the control signal generation circuit 1110. In anembodiment, the first input A1 1102 and the second input A2 1104 may beconnected to an external power supply directly (e.g., 1610 in FIG. 16).In an embodiment, the first input A1 1102 and the second input A2 1104may be connected in series to the external power supply through, e.g.,an external load.

The control signal generation circuit 1110 may be configured to detectone or more signals, and generate a control signal based on the detectedone or more signals. In some examples, the one or more signals may beone or more electrical signals received through electrical wires orcables. In some other examples, the one or more signals may be one ormore magnetic signals or other types of signals received by the magneticsensor 1105 wirelessly or by other means.

In operation, the control signal generation circuit 1110 determines,based on one or more detected signals, whether a predetermined conditionis satisfied. If the predetermined condition based on the one or moredetected signals, the control signal generation circuit 1110 maygenerate and transmit a first control signal to the output controlcircuit 1120 that will then accordingly control the magnetic sensor 1105to operate in a first state. In the first state, an electrical (load)current may flow out of the magnetic sensor to the output port B 1106.The control signal generation circuit 1110 may also generate andtransmit a second control signal to the output control circuit 1120 tocontrol the magnetic sensor 1105 to operate in a second state. In thesecond state, the electrical (load) current may flow from the outputport B 1106 into the magnetic sensor. How to determine the first stateor the second state at the control signal generation circuit isdescribed in further details.

On the other hand, when it is determined that the predeterminedcondition is not satisfied based on the one or more detected signals,the control signal generation circuit 1110 may generate and transmit athird control signal to the output control circuit 1120 to control themagnetic sensor 1105 to operate in a third state. In the third state, noelectrical (load) current flows through the output port B 1106. In somesituations in the third state, only a small amount of current flowsthrough the output port B 1106, e.g., the intensity of the current isless than one fourth of the electrical (load) current.

In some embodiment, the output control circuit 1120 is coupled with thecontrol signal generation circuit 1110 and configured to control themagnetic sensor 1105 to operate in a state determined based on thecontrol signal received from the control signal generation circuit 1110.For example, when the output control circuit 1120 receives the firstcontrol signal, the output control circuit 1120 controls the magneticsensor 1105 to operate in the first state in which the electrical (load)current flows out to the output port B 1106. When the output controlcircuit 1120 receives the second control signal, the output controlcircuit 1120 controls the magnetic sensor 1105 to operate in the secondstate in which the electrical (load) current flows from outside into themagnetic sensor via the output port B 1106. When the output controlcircuit 1120 receives the third control signal, the output controlcircuit 1120 controls the magnetic sensor 1105 to operate in the thirdstate in which no electrical (load) current flows through the outputport B 1106 (or only a small amount of current flows through whencompared with the electrical (load) current, e.g., such a current isless than one fourth of the electrical (load) current). In anembodiment, the output control circuit 1120 may alternately receive aplurality of control signals, including the first control signal and thesecond control signal, etc. Accordingly, the output control circuit 1120may control the magnetic sensor 1105 to operate alternately amongdifferent states. Specifically, the magnetic sensor 1150 may operatealternately between the first state and the second state. In anembodiment, when the magnetic sensor 1105 operates in the third state,the magnetic sensor 1105 may be prevented from operating in either thefirst state or the second state.

In an embodiment, when the first input A1 1102 and the second input A21104 are connected to the external AC power supply 1610 (FIG. 16), theoperating frequency of the magnetic sensor 1105, whether in the firststate, the second state, or the third state, may be set to be positivelyproportional to the frequency of the external AC power supply 1610. Inan embodiment, the operating frequency of the magnetic sensor 1105 inthe third state is twice of the operating frequency of the first stateor the second state, which is twice of the frequency of the external ACpower supply 1610.

FIG. 12 illustrates an exemplary diagram of the magnetic sensor 1105according to a different embodiment of the present teaching. In thisembodiment, the magnetic sensor 1105 comprises the first input A1 1102,the second input A2 1104, the output port B 1106, and an electroniccircuit 1100. The electronic circuit 1100 comprises a magnetic fielddetecting circuit 1130, a state control circuit 1140 coupled with themagnetic field detecting circuit 1130, and the output control circuit1120 coupled with the state control circuit 1140.

The magnetic field detecting circuit 1130 may be configured to detect anexternal magnetic field and output a magnetic induction signal inaccordance with the detected external magnetic field. The magneticinduction signal may indicate or represent the polarity and strength ofthe external magnetic field.

The state control circuit 1140 may be configured to determine whetherthe a predetermined condition is satisfied, and transmit a correspondingcontrol signal to the output control circuit 1120 based on thedetermination upon receiving the control signal, the output controlcircuit 1120 may control the magnetic sensor 1105 to operate in acorresponding state determined based on the magnetic induction signal.Specifically, when the predetermined condition is satisfied, thecorresponding state may be one of the first state and the second state,corresponding respectively to a specific polarity of the externalmagnetic field indicated by the magnetic induction signal. For example,the first state may correspond to a situation in which a first polarityof the external magnetic field is detected, and the second state maycorrespond to a situation in which a second polarity (which is oppositeto the first polarity) of the external magnetic field is detected.Accordingly, when the predetermined condition is satisfied and theexternal magnetic field exhibits a first polarity, the state controlcircuit 1140 may transmit a control signal indicating as such to theoutput control circuit 1120, according to which the output controlcircuit 1120 may control the magnetic sensor 1105 to operate in thefirst state. As described above, in the first state, the electrical(load) current flow from the magnetic sensor to outside via the outputport B 1106. When the predetermined condition is satisfied and theexternal magnetic field exhibits a second polarity that is opposite tothe first polarity, the state control circuit 1140 may transmit acontrol signal indicating as such to the output control circuit 1120,based on which the output control circuit 1120 may control the magneticsensor 1105 to operate in the second state. As described above, in thesecond state, the electrical (load) current flows from outside into themagnetic sensor via the output port B 1106.

On the other hand, when the state control circuit 1140 determines thatthe predetermined conditions is not satisfied (or when the state controlcircuit 1140 does not respond to the magnetic induction signal or cannotobtain the magnetic induction signal from the magnetic field detectingcircuit 1130), the state control circuit 1120 may transmit a controlsignal indicating as such to output control circuit 1120 to control themagnetic sensor 1105 to operate in a third state. In the third state, noelectrical (load) current flows through the output port B 1106 (or onlya small amount of current flows through the output port B compared withthe electrical (load) current, e.g., the intensity of the current isless than one fourth of the electrical (load) current).

The output control circuit 1120 is coupled with the control signalgeneration circuit 1110 and configured to control the magnetic sensor1105 to operate in a state determined based on a control signal receivedfrom the control signal generation circuit 1110. For example, when theoutput control circuit 1120 receives the control signal indicating thatthe predetermined condition is met and a first polarity of the externalmagnetic field, the output control circuit 1120 controls the magneticsensor 1105 to operate in the first state, allowing the electrical(load) current flow out of the magnetic sensor via the output port B1106. When the output control circuit 1120 receives the control signalindicating satisfaction of the predetermined condition and a secondpolarity detected from the external magnetic field, the output controlcircuit 1120 controls the magnetic sensor 1105 to operate in the secondstate, allowing the electrical (load) current flow from outside into themagnetic sensor via output port B 1106. When the output control circuit1120 receives the control signal indicating that the predeterminedcondition is not met, the output control circuit 1120 controls themagnetic sensor 1105 to operate in the third state, in which noelectrical (load) current may flow through the output port B 1106 (oronly a small amount of current flows through the output port B comparedwith the electrical (load) current above, e.g., the current is less thanone fourth of the electrical (load) current). In an embodiment, theoutput control circuit 1120 may receive alternately a plurality of thecontrol signals in time. Accordingly, the output control circuit 1120controls the magnetic sensor 1105 to operate among different statesalternately, including between the first state and the second state.

In an embodiment, the output control circuit 1120 may be configuredbased on a user's specification. For example, the output control circuit1120 may be configured to control the magnetic sensor 1105 to operatealternately between a working state and a high-impedance state. Theworking state may correspond to the first state or the second state, andthe high-impedance state may correspond to the third state.

FIG. 13 illustrates an exemplary diagram of the magnetic sensor 1105according to yet another embodiment of the present teaching. In thisembodiment, an exemplary construction of the magnetic field detectingcircuit 1130 is provided. The electronic circuit 1100, similar to FIG.12, includes the magnetic field detecting circuit 1130, the statecontrol circuit 1140, and the output control circuit 1120. The magneticfield detecting circuit 1130 in this embodiment comprises a magneticsensing element 1131, a signal processing element 1132, and ananalog-digital conversion element 1133.

The magnetic sensing element 1131 may be configured to detect and outputto the signal processing element an analog electrical signal that isindicative of certain information related to the external magneticfield. For example, the output of signal from the magnetic sensingelement 1131 may indicate the polarity of the external magnetic field.In an embodiment, the magnetic sensing element 1131 may be implementedbased on a Hall Board.

The signal processing element 1132 may be configured to process theanalog electrical signal from the magnetic sensing element 1131 andgenerate a processed analog electrical signal by, e.g. amplifying andreducing the interference of the analog electrical signals in order toimprove the accuracy of the detected signals. The processed analogelectrical signal is sent to the analog-digital conversion element 1133.

The analog-digital conversion element 1133 may be configured to convertthe processed analog electrical signal to a magnetic induction signal.In situations where only the polarity of the external magnetic fieldneeds to be detected, the magnetic induction signal may correspond to aswitching digital signal. The state control circuit 1140 and the outputcontrol circuit 1120 in FIG. 13 operate in the similar manner asdisclosed with respect to FIG. 12.

FIG. 14 illustrates an exemplary implementation of the output controlcircuit 1120 according to an embodiment of the present teaching. In anembodiment, the output control circuit 1120 may be configured accordingto a user's specification. As shown in FIG. 14, the output controlcircuit 1120 includes a first switch K1 1410, a second switch K2 1420,and a third switch K3 1430. Each of the first switch K1 1410, the secondswitch K2 1420, and the third switch K3 1430 is a diode or a transistor.The first switch is coupled with the output port B 1106 through thethird switch K3 1430 to form a first current path allowing the loadcurrent to flow through in a first direction. The second switch iscoupled with the output port B 1106 through the third switch K3 1430 toform a second current path allowing the load current to flow in a seconddirection opposite to the first direction. The first switch K1 1410 andthe second switch K2 1420 respond to the magnetic induction signal 1405to selectively turn on the corresponding current path.

In an embodiment, the first switch K1 1410 and the second switch K2 1420may be selectively turned on or off according to a user's specification.In an embodiment, the first switch K1 1410 and the second switch K2 1420may be configured to receive the magnetic induction signal 1405, whichindicates the detected polarity of the external magnetic field. Thefirst switch K1 1410 and the second switch K2 1420 may be selectivelyturned on or off in response to the magnetic induction signal 1405. Forexample, the first switch K1 1410 may be a high-voltage conductingswitch, and the second switch K2 1420 may be a low-voltage conductingswitch. To achieve that, the first switch K1 1410 is connected to ahigher voltage VDD 1407 (e.g., a direct current power supply), and thesecond switch K2 1420 is connected to a lower voltage (e.g., ground).When the magnetic induction signal 1405 has a high voltage, e.g.,indicating a first polarity detected from the external magnetic field,the first switch K1 1410 may be turned on and the second switch K2 1420may be turned off. When the magnetic induction signal 1405 has a lowvoltage, e.g., indicating a second polarity, opposite to the firstpolarity of the external magnetic field, the first switch K1 1410 may beturned off and the second switch K2 1420 may be turned on.

In an embodiment, the third switch K3 1430 may be turned on or off basedon whether the magnetic sensor 1105 satisfies the predeterminedcondition. For example, when the magnetic sensor 1105 satisfies thepredetermined condition, the third switch K3 1430 may be turned on.Otherwise, the third switch K3 1430 may be turned off. Details on how tocontrol the third switch is discussed with respect to FIG. 18.

As described above, when the magnetic sensor 1105 satisfies thepredetermined condition and the magnetic induction signal has a highvoltage, the first switch K1 1410 is turned on, the second switch K21420 is turned off, and the third switch K3 1430 is turned on.Accordingly, the first current path is on and the second current path isoff. As a result, the output control circuit 1120 controls the magneticsensor 1105 to operate in the first state. Namely, the electrical (load)current flows from the VDD 1407 through the first switch K1 1410, thethird switch K3 1430, and finally out of the output port B 1106.

When the magnetic sensor 1105 satisfies the predetermined condition andthe magnetic induction signal has a low voltage, the first switch K11410 is turned off, the second switch K2 1420 is turned on, and thethird switch K3 1430 is turned on. Accordingly, the first current pathis off and the second current path is on. As a result, the outputcontrol circuit 1120 may control the magnetic sensor 1105 to operate inthe second state. Namely, the electrical (load) current flows into theoutput port B 1106, through the third switch K3 1430, and the secondswitch K2 1420, to the ground.

When the magnetic sensor 1105 does not satisfies the predeterminedcondition, the third switch K3 1430 is turned off. Accordingly, neitherthe first current path nor the second current path is on. As a result,the output control circuit 1120 may control the magnetic sensor 1105 tooperate in the third state, no matter whether the magnetic inductionsignal 1405 has a high voltage or a low voltage. Namely, no electrical(load) current flows through the output port B 1106 (or only a smallamount of current flows through the output port B compared with theelectrical (load) current above, e.g., the current is less than onefourth of the electrical (load) current and cannot drive a load outsidethe magnetic sensor 1105). As such, the output control circuit 1120 doesnot respond to the magnetic induction signal 1405.

FIG. 15 illustrates an exemplary implementation of the output controlcircuit 1120 according to another embodiment of the present teaching. Asshown, the output control circuit 1120 is coupled with the magneticfield detecting circuit 1130. The output control circuit 1120 receivesthe magnetic induction signal 1405 (as shown in FIG. 14) from themagnetic field detecting circuit 1130. The output control circuit 1120includes a single-conducting switch D 1510, a resistor R 1520, and thethird switch K3 1430. The single-conducting switch D 1510 is coupledwith the output port B 1106 through the third switch K3 1340, forming afirst current path allowing the load current to flow in a firstdirection. On the other hand, the resistor R 1520 is coupled with theoutput port B 1106 through the third switch K3 1430, forming a secondcurrent path allowing the load current to flow in a second directionopposite to the first direction. When the magnetic sensor 1105 satisfiesthe predetermined condition, the third switch K3 1430 may be turned on.Otherwise, the third switch K3 1530 may be turned off. Details on how tocontrol the on/off of the third switch is discussed with respect to FIG.18. The single-conducting switch D 1510 may be selectively turned on oroff based on the magnetic induction signal 1405 received from themagnetic field detecting circuit 1130. For example, when the magneticinduction signal 1405 has a high voltage, the single-conducting switch D1510 is turned on. When the magnetic induction signal 1405 has a lowvoltage, the single-conducting switch D 1510 is turned off. In anotherembodiment, the resistor R 1520 may be replaced by anothersingle-conducting switch connected anti-parallel with thesingle-conducting switch D 1510.

As described above, when the magnetic sensor 1105 satisfies thepredetermined condition and the magnetic induction signal 1405 receivedfrom the magnetic field detecting circuit 1130 has a high voltage, boththe single-conducting switch D 1510 and the third switch K3 1430 areturned on. Accordingly, the first current path is on and the secondcurrent path is off. As a result, the output control circuit 1120 maycontrol the magnetic sensor 1105 to operate in the first state. Namely,the electrical (load) current flows out of the output port B 1106through the single-conducting switch D 1510 and the third switch K31530.

When the magnetic sensor 1105 satisfies the predetermined condition andthe magnetic induction signal 1405 received from the magnetic fielddetecting circuit 1130 has a low voltage, the single-conducting switch D1510 is turned off and the third switch K3 1430 is turned on.Accordingly, the first current path is off. As the magnetic inductionsignal is low, and the third switch K3 1430 is on, the second currentpath is conducting. As a result, the output control circuit 1120 maycontrol the magnetic sensor 1105 to operate in the second state. Namely,the electrical (load) current flows into the output port B 1106, andthrough the third switch K3 1530 and the resistor R 1520, respectively.

When the magnetic sensor 1105 does not satisfies the predeterminedcondition, the third switch K3 1430 is turned off. In this case, neitherthe first current path nor the second current path is on. As a result,the output control circuit 1120 may control the magnetic sensor 1105 tooperate in the third state no matter whether the magnetic inductionsignal 1405 has a high voltage or a low voltage. Namely, no electrical(load) current flows through the output port B 1106. As such, the outputcontrol circuit 1120 does not respond to the magnetic induction signal1405.

FIG. 16 illustrates another exemplary diagram of the magnetic sensor1105 according to yet another embodiment of the present teaching. Asshown, the input 1615 of the magnetic sensor 1105 is connected to anexternal AC power supply 1610. In this embodiment, the magnetic sensor1105 includes a rectifier 1150 connected to the input 1615 andconfigured to receive a pair of differential AC signals from theexternal AC power supply 1610 and convert the pair of differential ACsignals to direct current (DC) signals. The output voltage of therectifier 1150 may be used to power up the magnetic field detectingcircuit 1130, the state control circuit 1140, and the output controlcircuit 1120. The magnetic sensor 1105 may further comprise the magneticdetecting circuit 1130, the state control circuit 1140, and the outputcontrol circuit 1120, as described above.

FIG. 17 illustrates an exemplary diagram of the rectifier 1150 accordingto an embodiment of the present teaching. The rectifier 1150 includes afull wave rectifier bridge and a stabilizing unit connected to the fullwave rectifier. The full wave rectifier bridge includes a first diode D11710, a second diode D2 1720, a third diode D3 1730, and a fourth diodeD4 1740. As shown in FIG. 17, the first diode D1 1710 is connected inseries to the second diode D2 1720, and the third diode D3 1730 isconnected in series to the fourth diode D4 1740. The output of the firstdiode D1 1710 and the input of the second diode D2 1720 are connected tothe first input port VAC+ 1705, and the output of the third diode D31730 and the input of the fourth diode D4 1740 are connected to thesecond input port VAC− 1707. In an embodiment, the first input port VAC+1705 and the second input port VAC− 1707 are a pair of differential ACsignals. The full wave rectifier bridge may be configured to convert thepair of differential AC signals outputted by the AC power supply 1610 todirect signals. The stabilizing unit may be a Zener diode DZ 1750 andconfigured to stabilize the direct signals outputted by the full waverectifier bridge within a predetermined range. The stabilizing unitoutputs a stabilized DC voltage.

In an embodiment, the input of the first diode D1 1710 is connected tothe input of the third diode D3 1730 at a first connection point,thereby forming the grounded port of the full wave rectifier bridge. Inaddition, the output of the second diode D2 1720 is connected to theoutput of the fourth diode D4 1740 at a second connection point, therebyforming the output port of the full wave rectifier bridge, VDD 1760. TheZener diode DZ 1750 is situated between the first connection point andthe second connection point. In an embodiment, the output VDD 1760 maybe connected directly with the output control circuit 1120.

In an embodiment, the first input port VAC+ 1705 and the second inputport VAC− 1707 are connected to the external AC power supply 1610. Inthis case, the output control circuit 1120 may respond to the polarityof the external AC power supply 1610 in addition to the magneticinduction signal 1405.

In an embodiment, whether the magnetic sensor 1105 operates in the firststate, the second state, or the third state, depends on whether themagnetic sensor 1105 satisfies the predetermined condition, which may bedetermined according to a user's specification. Accordingly, the outputcontrol circuit 1120 may control the magnetic sensor 1105 to operate inthe first state that the electrical (load) current may flow out of theoutput port B 1106 or in the second state that the electrical (load)current may flow into the output port B 1106. Alternatively oradditionally, when the magnetic sensor 1105 satisfies the predeterminedcondition, the output control circuit 1120 may control the magneticsensor 1105 to operate alternately between the first state and thesecond state in response to the polarity of the external AC power supply1610 and the polarity of the magnetic field indicated by the magneticinduction signal 1405. When the magnetic sensor 1105 does not satisfythe predetermined condition, the output control circuit 1120 may controlthe magnetic sensor 1105 to operate in the third state that noelectrical (load) current may flow through the output port B 1106 oronly a small amount of current flows through the output port B comparedwith the electrical (load) current above, e.g., the intensity of thecurrent is less than one fourth of the electrical (load) current.

In an embodiment, when the magnetic sensor 1105 satisfies thepredetermined condition, the output control circuit 1120 may respond toboth the magnetic induction signal and the external AC power supply 1610to further control the magnetic sensor 1105 to operate in the firststate or the second state. For example, when the magnetic sensor 1105satisfies the predetermined condition and the magnetic induction signal1405 indicates that the external magnetic field has the first magneticpolarity and the external AC power supply 1610 has the first electricpolarity, the output control circuit 1120 may control the magneticsensor 1105 to operate in the first state. For another example, when themagnetic sensor 1105 satisfies the predetermined condition and themagnetic induction signal 1405 indicates that the external magneticfield has the second magnetic polarity which is opposite to the firstmagnetic polarity and the AC power supply 1610 has the second electricpolarity which is opposite to the first electric polarity, the outputcontrol circuit 1120 may control the magnetic sensor 1105 to operate inthe second state.

FIG. 18 illustrates an exemplary diagram of the magnetic sensor 1105according to yet another embodiment of the present teaching. In thisexemplary embodiment, an exemplary construction of the state controlcircuit 1140 is provided. As shown, the input 1615 of the magneticsensor 1105 is connected to an external AC power supply 1610. As shownbefore, the magnetic sensor 1105 includes a rectifier 1150 connected tothe input 1615 and configured to receive a pair of differential ACsignals from the external AC power supply 1610 and convert the pair ofdifferential AC signals to direct current signals. The magnetic sensor1105 further comprises the magnetic detecting circuit 1130, the statecontrol circuit 1140, and the output control circuit 1120. As shown inFIG. 18, the state control circuit 1140 further comprises a voltagedetecting circuit 1142, a delay circuit 1141, and a logic circuit 1143.

The voltage detecting circuit 1142 may be configured to detect whether avoltage in the magnetic sensor 1105 equals to or exceeds a thresholdvoltage. When the voltage exceeds the threshold voltage, the voltagedetecting circuit 1142 generates a predetermined trigger signal andtransmits it to the delay circuit 1141. In an embodiment, the voltagemay be the supply voltage of the magnetic field detecting circuit 1130.The threshold voltage may be the minimal voltage required for theoperation of the magnetic sensing element 1131, the signal processingelement 1132, and the analog-digital conversion element 1133 of themagnetic field detecting circuit 1130. In an embodiment, the thresholdvoltage may set to be a value that is smaller than the stabilized DCvoltage achieved by the stabilizing unit as described with respect toFIG. 17.

Once being triggered by the voltage detecting circuit 1142, the delaycircuit 1141 determines whether the magnetic sensor 1105 satisfies thepredetermined condition. Specifically, the delay circuit 1141 may startto time, upon the receipt of the predetermined trigger signal from thevoltage detecting circuit 1142. When the timed period is equal to orlonger than a predetermined length of period, the delay circuit 1141determines that the magnetic sensor 1105 satisfies the predeterminedcondition. Otherwise, the delay circuit 1141 determines that themagnetic sensor 1105 does not satisfy the predetermined condition.

The logic circuit 1143 may be configured to enable the output controlcircuit 1120 to respond to the magnetic induction signal and control themagnetic sensor 1105 to operate in any of the three states in the manneras discussed herein. For example, the magnetic sensor will operate inthe first state or the second state when the timed period recorded bythe delay circuit 1141 is equal to or greater than the predeterminedperiod. The logic circuit 1143 is further configured to enable theoutput control circuit 1120 to control the magnetic sensor 1105 tooperate in the third state when the timed period recorded by the delaycircuit 1141 is less than the predetermined period.

In an embodiment, to detect that the supply voltage of the magneticfield detecting circuit 1130 reaches the predetermined voltage thresholdis to ensure that all the modules of the magnetic field detectingcircuit 1130, i.e., the magnetic sensing element 1131, the signalprocessing element 1132, and the analog-digital conversion element 1133,may function normally.

FIG. 19 illustrates an exemplary implementation circuit of a part of themagnetic sensor 1105 according to yet another embodiment of the presentteaching. Specifically, FIG. 19 illustrates an exemplary implementationof the output control circuit 1120 and the state control circuit 1140.The state control circuit 1140 includes the voltage detecting circuit1142, the delay circuit 1141, and the logic circuit 1143, which is anAND gate 1910 as shown in FIG. 19. A first input of the AND gate 1910may correspond to the magnetic induction signal 1905, a second input ofthe AND gate 1910 may be connected to an output of the delay circuit1141, and the output of the AND gate 1910 may be connected to the outputcontrol circuit 1120.

In this embodiment, the output control circuit 1120 includes threehigh-voltage conducting switches M0 1920, M1 1960, M2 1970, a diode D51980, an inverter 1990, a first resistor R1 1930, and a second resistorR2 1950. The control terminal of the switch M0 1920 is connected to theoutput of the AND gate 1910. The input of the switch M0 1920 isconnected to a voltage output port 1940 (OUTAD+) of the rectifier 1150through the resistor R1 1930. The switch M2 1970 is coupled in parallelwith the switch M0 1920. The control terminal of the switch M2 1970 isconnected to the output of the delay circuit 1141 through the inverter1990. In an embodiment, the equivalent resistance of the switch M2 1970is greater than that of the switch M0 1920.

In operation, when the timed period recorded by the delay circuit 1141is equal to or longer than the predetermined threshold period, the delaycircuit 1141 outputs a high voltage. Accordingly, this high voltageallows the magnetic induction signal 1905 from the magnetic fielddetecting circuit 1130 is transmitted to the switch M0 1920 through theAND gate 1910. In addition, when the signal from the AC power supply1610 is in the positive half cycle and the magnetic induction signal1905 from the magnetic field detecting circuit 1130 outputs low voltage,the switch M0 1920 and the switch M2 1970 may be turned off, and theswitch M1 1960 may be turned on. As a result, the electrical (load)current may flow out of the output port B 1106 through the switch M11960. Namely, the output control circuit 1120 operates the magneticsensor 1105 in the first state. Alternatively, when the signal from theAC power supply 1610 is in the negative half cycle and the magneticinduction signal 1905 from the magnetic field detecting circuit 1130outputs high voltage, the switch M0 1920 may be turned on, and theswitches M1 1960 and M2 1970 may be turned off. As a result, theelectrical (load) current may flow into the output port B 1106 and passthrough the diode D5 1980 and the switch M0 1920. Namely, the outputcontrol circuit 1120 may control the magnetic sensor 1105 to operate inthe second state.

When the timed period recorded by the delay circuit 1141 is shorter thanthe threshold period. The delay circuit 1141 and the AND gate 1910 mayoutput a low voltage, the switches M0 1920 and M1 may be turned off, andthe switch M2 1970 may be turned on. As a result, the electrical currentflows into the output port B 1106 and passes through the diode D5 1980and the switch M2 1970. Since the equivalent resistance of the switch M21970 is large, the electrical current is very small, or negligible. Thatis, the output control circuit 1120 controls the magnetic sensor 1105 tooperate in the third state.

FIG. 20 illustrates another embodiment of the output control circuit1120 in connection with the state control circuit 1140. The statecontrol circuit 1140 includes the voltage detecting circuit 1142, thedelay circuit 1141, and the logic circuit 1143. Specifically, the logiccircuit 1143 of the state control circuit 1140 includes a first signalinput port 2002, a second signal input port 2004, a first signal outputport 2006, and a second signal output port 2008. The first signal inputport 2002 may be connected to the output of the delay circuit 1141, andthe second signal input port may be connected to receive the magneticinduction signal 2005. When the timed period recorded by the delaycircuit 1141 is shorter than the threshold period, the logic circuit1143 may be configured to output a low voltage as the delay circuit1141. On the other hand, when the timed period recorded by the delaycircuit 1141 is equal to or longer than the threshold period, the delaycircuit 1141 may output high voltage. Further, the logic circuit 1143may output the magnetic induction signal 2005 through the first signaloutput port 2006 or the second signal output port 2008. The outputsignals in the first signal output port 2006 and the second signaloutput port 2008 may have a 180 degree phase difference. It should beappreciated that the output signals in the first output port 2006 andthe second output port 2008 cannot have high voltages at the same time.

In this embodiment, the output control circuit 1120 includes threeswitches, i.e., switches M3 2060, M4 2040, and M5 2070, two resistances,i.e., resistances R3 2050, and R4 2030, and a protecting diode D6 2020.Specifically, the switches M3 2060 and M5 2070 are both high-voltageconducting switches, and the switch M4 2040 is a low-voltage conductingswitch. The control terminals of the switch M3 2060 and the switch M52070 are connected to the first signal output port 2006 and the secondsignal output port 2008 of the logic circuit 1143, respectively. Theinput of the switch M3 2060 is connected to a first port of the resistorR3 2050. The output of the switch M3 2060 is connected to the groundedoutput (OUTAD− 2080) of the rectifier 1150 (as shown in FIG. 15).

The control terminal of the switch M4 2040 is connected to a second portof the resistor R3 2050. The input of the switch M4 2040 is connected tothe voltage output port (OUTAD+ 2010) of the rectifier 1150. The outputof the switch M4 2040 is connected to the input of the switch M5 2070.The output of the switch M5 2070 is connected to the voltage output port(OUTAD− 2080) of the rectifier 1150. In an embodiment, the voltageoutput port (OUTAD− 2080) is a floating ground. The output of the switchM4 2040 is connected to the input of the switch M5 2070 and the outputport B 1106. The control terminal of the switch M4 2040 is connected tothe positive polarity of the protecting diode D6 2020. The input of theswitch M4 2040 is connected to the negative polarity of the protectingdiode D6 2020. The resistor R4 2030 is connected between the controlterminal and input terminal of the switch M4 2040.

In operation, when the timed period recorded by the delay circuit 1141is equal to or longer than the threshold period, the delay circuit 1141outputs a high voltage. In this case, the logic circuit 1143 allows themagnetic induction signal be output through the first signal output port2006 or the second signal output port 2008. The output signals in thefirst signal output port 2002 and the second signal output port 2004 mayhave a 180 degree phase difference. In addition, when the signal fromthe AC power supply 1610 is in the positive half cycle and the magneticinduction signal 2005 from the magnetic field detecting circuit 1130corresponds to a high voltage, the switches M3 2060 and M4 2040 may beturned on, the switch M5 2070 may be turned off. As a result, theelectrical (load) current flows out of the output port B 1106 throughthe switch M4 2040. Namely, the output control circuit 1120 controls themagnetic sensor 1105 to operate in the first state. Alternatively, whenthe signal from the AC power supply 1610 is in the negative half cycleand the magnetic induction signal 2005 from the magnetic field detectingcircuit 1130 corresponds to a low voltage, the switches M3 2060 and M42040 may be turned off, and the switch M5 2070 may be turned on. As aresult, the electrical current flows into the output port B 1106 andpasses through the switch M5 2070. Namely, the output control circuit1120 controls the magnetic sensor 1105 to operate in the second state.

When the timed period recorded by the delay circuit 1141 is shorter thanthe threshold period, the output control circuit 1120 is designated tocontrol the magnetic sensor 1105 to operate in the third state. In thiscase, the delay circuit 1141 outputs a low voltage, the logic circuit1143 outputs a low voltage at each of the first output port 2006 and thesecond output port 2008, and the switches M3 2060, M4 2040, and M5 2070may be turned off. As a result, no electrical current flows through theoutput port B 1106 (or only a small amount of current flows through theoutput port B compared with the electrical (load) current above, e.g.,the current is less than one fourth of the electrical (load) current).

FIG. 21 is a flowchart of an exemplary method of signal processingperformed by the magnetic sensor 1105, according to an embodiment of thepresent teaching. At step S101, an external magnetic field is detected.A magnetic induction signal may be indicative of the polarity and/orstrength of the external magnetic field is generated. Specifically, atstep S101, analog electrical signals associated with an externalmagnetic field and information associated therein are detected andoutputted. In addition, the detected analog electrical signal may beprocessed by amplifying and reducing interference of the analogelectrical signal. Further, the processed analog electrical signal maybe converted to generate the magnetic induction signal. In someapplications, the magnetic induction signal may be a switch digitalsignal that is indicative of the polarity of the external magneticfield.

At step S102, it is determined whether a predetermined condition issatisfied. The predetermined condition is related or assessed withrespect to a specific voltage of the magnetic sensor. If thepredetermined condition is met, the method proceeds to step S103.Otherwise, the method proceeds to step S104. Specifically, thepredetermined condition may be set as a predetermined period that thevoltage of the magnetic sensor reaches the predetermined voltagethreshold. In an embodiment, whether the predetermined condition issatisfied may be determined based on the period of time during which thevoltage of the magnetic sensor 1105 is equal to or above a predeterminedvoltage threshold. As discussed herein, to perform step S102, it isdetermined whether the voltage of the magnetic sensor 1105 reaches thepredetermined voltage threshold. If so, the delay circuit 1141 starts totime. If the timed period reaches a predetermined length, it isdetermined that the predetermined condition is satisfied. Otherwise, itis determined that the predetermined condition is not satisfied.

At step S103, based on the magnetic induction signal, the magneticsensor is controlled to operate in at least one of a first state and asecond state. As discussed herein, in the first state, an electrical(load) current flows out of the output port B 1106. In the second state,the electrical (load) current flows into the output port B 1106. At stepS104, the magnetic sensor is controlled to operate in a third state, inwhich the magnetic sensor 1105 operates in neither the first state northe second state, i.e., no current (or negligible) flows through theoutput port B 1106.

FIG. 22 illustrates an exemplary diagram of a motor assembly 2200incorporating the magnetic sensor discussed herein, according to anembodiment of the present teaching. The motor assembly 2200 comprises amotor M 1202 coupled with an external AC power supply 1610, acontrollable bi-directional AC switch 1300 coupled in series with themotor M 1202, and the magnetic sensor 1105. The magnetic sensor 1105resides close to the rotor of the motor 1202 in order to detect thevariation of the magnetic field near the rotor.

In an embodiment, the magnetic sensor 1105 includes a first input 1102coupled to the motor 1202, a second input 1104 coupled to the externalAC power supply 1610, and the output 1106 coupled to a control terminalof the controllable bi-directional AC switch 1105.

In an embodiment, the motor assembly 2200 may further comprise a voltagereducing circuit 1105, configured to e.g., provide a reduced voltageobtained based on the AC power supply 1610, to the magnetic sensor 1105.In this embodiment, the first input 1102 of the magnetic sensor 1105 isinstead coupled to the voltage reducing circuit 1200.

FIG. 23 illustrates an exemplary diagram of a motor 2300 according to anembodiment of the present teaching. The motor 2300 may be similar to themotor 1202 in FIG. 22. In an embodiment, the motor 2300 is a synchronousmotor including a stator and a rotor M1 rotating around the stator. Thestator includes a stator core M2 and a single phase winding M3 windingaround the stator core M2. The stator core M2 may include pure iron,cast iron, cast steel, electrical steel, silicon steel, or any othersoft magnetic materials. The rotor M1 includes a permanent magnet. Whenthe stator winding M3 is coupled in series with the AC power supply1610, the rotor M1 may operate at a uniform speed of 60 f/prevolution/minute (rmp) in the stable phase, where f is the frequency ofthe AC power supply 1610, and p is the number of pole pairs of the rotorM1. The stator core M2 has two opposite polarities, either of which hasa pole arc (e.g., M4, M5). The outer surface of the rotor M1 is oppositeto the pole arc (e.g., M4, M5), thereby forming a non-uniform gapbetween the outer surface and the pole arc. The pole arcs (e.g., M4, M5)of the stator poles are embedded with concave grooves. The portion ofthe pole arc other than the concave groove has the same center axis asthe rotor M1.

A non-uniform magnetic field may be formed in the above configuration,which ensures that the polar of the rotor M1 is relative to the centeraxis of the stator pole with an angle when the rotor M1 is static. Theangle ensures an initial torque for the rotor M1 every time the motor Mis powered up under the influence of the magnetic sensor 1105. The polarof the rotor M1 may be the boundary between the opposite magneticpolarities of the rotor M1. The center axis of the stator may be a linepassing through the centers of the poles of the stator. In anembodiment, both the stator and the rotor M1 have two magneticpolarities. In an embodiment, the stator and the rotor M1 may have agreater number of magnetic polarities, e.g., four or six magneticpolarities.

Returning to FIG. 22, when the magnetic sensor 1105 satisfies thepredetermined condition, the magnetic sensor 1105 may operate in eitherthe first state or the second state depending on the signal from the ACpower supply 1610 and the polarity of the permanent magnetic rotor M1.Specifically, when the signal from the AC power supply 1610 is in thepositive half cycle and the magnetic field detecting circuit 1130detects that the permanent magnetic rotor M1 has a first polarity, theoutput control circuit 1120 controls the magnetic sensor 1105 to operatein the first state. Namely, an electrical current may flow from themagnetic sensor 1105 to the controllable bi-directional AC switch 1300.Alternatively, when the signal from the AC power supply 1610 is in thenegative half cycle and the magnetic field detecting circuit 1130detects that the permanent magnetic rotor M1 has a second polarity thatis opposite to the first polarity, the output control circuit 1120controls the magnetic sensor 1105 to operate in the second state, inwhich, the electrical current may flow from the controllablebi-directional AC switch 1300 to the magnetic sensor 1105.

When the magnetic sensor 1105 does not satisfy the predeterminedcondition, the magnetic sensor 1105 operates in the third state, inwhich, no electrical current flows between the controllablebi-directional AC switch 1300 and the magnetic sensor 1105 (or only asmall amount of current flows between the controllable bi-directional ACswitch 1300 and the magnetic sensor 1105).

In an embodiment, the magnetic sensor 1105 includes the rectifier 1150as shown in FIG. 17 and the output control circuit 1120 as shown in FIG.14. As described above, in FIG. 14, the output control circuit 1120includes the first switch K1 1410 which is a high-voltage conductingswitch, the second switch K2 1420 which is a low-voltage conductingswitch, and the third switch K3 1430. When the predetermined conditionis met, the third switch K3 1430 is turned on. In addition, when thesignal from the AC power supply 1610 is in the positive half cycle andthe magnetic induction signal is a high voltage, the first switch K11410 is turned on and the second switch K2 1420 is turned off. As aresult, the magnetic sensor 1105 operates in the first state, in which,the electrical current flows from the AC power supply 1610, through themotor M 1202, voltage reducing circuit 1105, the first input port of themagnetic sensor 1105, the voltage output port of the second diode D2 inthe full wave rectifier bridge, the first switch K1 1410 of the outputcontrol circuit 1120, the output port B 1106, then the controllablebi-directional AC switch 1105, finally back to the AC power supply 1610.Alternatively, when the signal from the AC power supply 1610 is in thenegative half cycle and the magnetic induction signal is a low voltage,the first switch K1 1410 is turned off and the second switch K2 1420 isturned on. As a result, the magnetic sensor 1105 operates in the secondstate, in which, the electrical current flows from the AC power supply1610, through the controllable bi-directional AC switch 1105, the outputport B 1106, the second switch K2 1420, the grounded port of the fullwave rectifier bridge, the first diode D1 1710, the first input port ofthe magnetic sensor 1105, the voltage reducing circuit 1105, the motor1202, and finally back to the AC power supply 1610.

When the signal from the AC power supply 1610 is in the positive halfcycle and the magnetic field detecting circuit 1130 outputs a lowvoltage, or when the signal from the AC power supply 1610 is in thenegative half cycle and the magnetic field detecting circuit 1130outputs a high voltage, neither the first switch K1 1410 nor the secondswitch K2 1420 can be turned on. Therefore, the output control circuit1120 operates the controllable bi-directional AC switch 1105 alternatelybetween “ON” and “OFF” states in a predetermined manner. The outputcontrol circuit 1120 may further enable the magnetic sensor 1105 tocontrol the way of powering up the stator winding M3 based on thevariation of the polarity of the AC power supply 1610 and the magneticdetection information, rendering the varying magnetic field generated bythe stator to rotate along with the rotor in a single direction inaccordance with the position of the magnetic field of the rotor. Thisenables that the rotor M1 to rotate in the fixed direction every timethe motor 1202 is powered up.

On the other hand, when the magnetic sensor 1105 does not satisfy thepredetermined condition, the third switch K3 1430 is turned off. As aresult, the magnetic sensor 1105 operates in the third state, in which,no electrical current flows in the motor assembly 2200 (or only a smallnegligible amount of current flows in the motor assembly 2200) comparedwith the electrical current above, e.g., the intensity of the current isless than one fourth of the electrical current.

FIG. 24 illustrates the waveforms of an output voltage from an AC powersupply 1610 and the rectifier bridge 1150, respectively, according to anembodiment of the present teaching. Specifically, the upper portion ofFIG. 24 illustrates the waveform of the output voltage from the AC powersupply 1610, and the lower portion of FIG. 24 illustrates the waveformof the output voltage of the rectifier bridge 1150. As shown, thefrequency of the output voltage of the rectifier bridge is twice of thefrequency of the AC power supply 1610.

When the waveform of the output voltage of the rectifier bridge 1150rises, the output control circuit 1120 may operate in the third statebefore the output control circuit 1120 operates in the first state orthe second state. Accordingly, when the waveform of the output voltageof the AC power supply 1610 is in the positive half cycle, the magneticsensor 1105 may operate in the first state. When the waveform of theoutput voltage of the AC power supply 1610 is in the negative halfcycle, the magnetic sensor 1105 may operate in the second state.Therefore, the operating frequency of the third state is positivelyproportional to the operating frequency of the first state or the secondstate, and is also proportional to the frequency of voltage of the ACpower supply 1610. In an embodiment, the operating frequency of thethird state is twice of the operating frequency of the first state orthe second state, which is twice of the frequency of the AC power supply1610.

It should be appreciated that the examples described above are forillustrative purpose. The present teaching is not intended to belimiting. The magnetic sensor 1105 may be used in applications otherthan the motor assembly 2200 as described above.

Returning to FIG. 22, in an embodiment, the motor 1202 and thecontrollable bi-directional AC switch 1300 may be coupled in series witheach other and form a first branch. The series-connected voltagereducing circuit 1200 and the magnetic sensor 1105 form a second branch.The first branch is coupled in parallel with the second branch betweentwo ends of the external AC power supply 1610.

Those skilled in the art will recognize that the present teachings areamenable to a variety of modifications and/or enhancements. For example,although the implementation of various components described above may beembodied in a hardware device, it can also be implemented as a softwareonly solution—e.g., an installation on an existing server. In addition,the units of the host and the client nodes as disclosed herein can beimplemented as a firmware, firmware/software combination,firmware/hardware combination, or a hardware/firmware/softwarecombination.

While the foregoing has described what are considered to be the bestmode and/or other examples, it is understood that various modificationsmay be made therein and that the subject matter disclosed herein may beimplemented in various forms and examples, and that the teachings may beapplied in numerous applications, only some of which have been describedherein. It is intended by the following claims to claim any and allapplications, modifications and variations that fall within the truescope of the present teachings.

We claim:
 1. A magnetic sensor, comprising: a housing; an input port andan output port, both extending from the housing, wherein the input portis to be connected to an external alternating current (AC) power supply;and an electrical circuit which comprises: an output control circuitcoupled with the output port and configured to be at least responsive toa magnetic induction signal and, when a predetermined condition issatisfied, to control the magnetic sensor to operate in at least one ofa first state and a second state, the predetermined condition being setas a predetermined period that a voltage of the magnetic sensor reachesa predetermined voltage threshold, wherein: in the first state, a loadcurrent flows in a first direction from the output port to outside ofthe magnetic sensor, in the second state, a load current flows in asecond direction opposite that of the first direction from outside ofthe magnetic sensor into the magnetic sensor via the output port, and anoperating frequency of the magnetic sensor is positively proportional toa frequency of the external AC power supply; and a sub-circuitconfigured to determine whether the predetermined condition issatisfied, the sub-circuit further comprising: a voltage detectingcircuit configured to detect a specific voltage and, when the specificvoltage equals to or is greater than a predetermined voltage threshold,output a triggering signal; a delay circuit coupled with the voltagedetecting circuit and configured to time, upon receiving the triggeringsignal, a length of time during which the specific voltage equals to oris greater than the predetermined voltage threshold; and a logic circuitcoupled with the delay circuit and configured to: signal that thepredetermined condition is satisfied, when the length of time exceeds apredetermined length of time, and signal that the predeterminedcondition is not satisfied, when the length of time does not exceed thepredetermined length of time.
 2. The magnetic sensor of claim 1, whereinthe electrical circuit further comprises: a magnetic field detectingcircuit configured to detect an external magnetic field and output themagnetic induction signal that is indicative of at least onecharacteristic of the external magnetic field.
 3. The magnetic sensor ofclaim 2, wherein the magnetic field detecting circuit comprises: amagnetic sensing element configured to detect the external magneticfield and output an analog electric signal that corresponds to theexternal magnetic field; a signal processing element configured toamplify the analog electric signal, remove interference therefrom, andgenerate a processed analog electric signal; and an analog-digitalconversion element configured to convert the processed analog electricsignal to the magnetic induction signal, which corresponds to aswitching digital signal.
 4. The magnetic sensor of claim 1, wherein,when the predetermined condition is satisfied, the magnetic sensoroperates alternately between the first and the second state, dependingon a magnetic polarity of the external magnetic field and a polarity ofthe external AC power supply.
 5. The magnetic sensor of claim 4, whereinthe output control circuit is configured to control the magnetic sensor,when the predetermined condition is satisfied, to operate in the firststate by allowing a load current to flow in the first direction when themagnetic induction signal indicates that the external magnetic field hasa first magnetic polarity and the external AC power supply has a firstpolarity; and in the second state by allowing a load current to flow inthe second direction when the magnetic induction signal indicates thatthe external magnetic field has a second magnetic polarity opposite tothe first magnetic polarity and the external AC power supply has asecond polarity opposite to the first polarity.
 6. The magnetic sensorof claim 1, wherein the output control circuit comprises a first switchcoupled with the output port to form a first current path for a loadcurrent to flow in the first direction; and a second switch coupled withthe output port to form a second current path for a load current to flowin the second direction, wherein the first and second switches respondrespectively to the magnetic induction signal to selectively turn on thefirst and second current paths, respectively.
 7. The magnetic sensor ofclaim 1, wherein when the magnetic sensor operates in either the firstor the second state, the operating frequency of the magnetic sensor isthe same as the frequency of the external AC power supply.
 8. Themagnetic sensor of claim 1, wherein the output control circuit isfurther configured to control, when the predetermined condition is notsatisfied, the magnetic sensor to operate in a third state, in whichthere is no or a negligible amount of load current flowing through theoutput port.
 9. The magnetic sensor of claim 8, wherein the operatingfrequency of the magnetic sensor in the third state is twice of thefrequency of the external AC power supply.
 10. The magnetic sensor ofclaim 1, wherein the electrical circuit further comprises a rectifierconfigured to rectify in full wave the external AC power supply togenerate an output voltage having a frequency twice of the operatingfrequency of the magnetic sensor in the first or the second state.
 11. Amagnetic sensor, comprising a housing; an input port extending from thehousing and coupled with an external alternating current (AC) powersupply; an output port extending from the housing; and an electricalcircuit which comprises: an output control circuit coupled with theoutput port and configured to be at least responsive to a magneticinduction signal, the external AC power supply and, when a predeterminedcondition is satisfied, to control the magnetic sensor to operate in afirst state in which a load current flows through the output port and asecond state in which the load current flows to the magnetic sensor fromthe output port, the predetermined condition being set as apredetermined period that a voltage of the magnetic sensor reaches apredetermined voltage threshold, the output control circuit comprising:a sub-circuit configured to determine whether the predeterminedcondition is satisfied, the sub-circuit further comprising: a voltagedetecting circuit configured to detect a specific voltage and, when thespecific voltage equals to or is greater than a predetermined voltagethreshold, output a triggering signal; a delay circuit coupled with thevoltage detecting circuit and configured to time, upon receiving thetriggering signal, a length of time during which the specific voltageequals to or is greater than the predetermined voltage threshold; and alogic circuit coupled with the delay circuit and configured to:  signalthat the predetermined condition is satisfied, when the length of timeexceeds a predetermined length of time, and  signal that thepredetermined condition is not satisfied, when the length of time doesnot exceed the predetermined length of time, wherein the magneticinduction signal is indicative of at least one characteristic of anexternal magnetic field detected by the electrical circuit, and theoperating frequency of the magnetic sensor is positively proportional tothe frequency of the external AC power supply.